[R] on lexical scoping....

[akshay kulkarni]

dear Bert,
                  I could predict most of them, but,of course, you have not wasted my time!

Thanking you,
Yours sincerely,
AKSHAY M KULKARNI
________________________________
From: Bert Gunter <bgunter.4567 using gmail.com>
Sent: Wednesday, April 5, 2023 4:36 AM
To: akshay kulkarni <akshay_e4 using hotmail.com>
Cc: R help Mailing list <r-help using r-project.org>
Subject: Re: [R] on lexical scoping....

The following *might* be of use to you. If you can predict what the various function invocations will do, I think you have a reasonable grasp of how lexical scoping works in R (contrary or supplementary opinions welcome).  It is the sort of thing you will find in the references also. If this is all obvious, sorry for wasting your time.
#######################
search()
ls()
dat <- list(x =2)
attach(dat,2)
search()
f <- function(){
   g <- function() x
   x <- 3
   g}
h <- f()
g <- function()x
ls()
h()
g()
detach(dat)
h()
g()

##########################
## Here is what this gives starting with an empty .GlobalEnv.
##################################

> search()
 [1] ".GlobalEnv"        "package:tools"     "package:lattice"   "tools:rstudio"
 [5] "package:stats"     "package:graphics"  "package:grDevices" "package:utils"
 [9] "package:datasets"  "package:methods"   "Autoloads"         "package:base"
> ls()
character(0)
> dat <- list(x =2)
> attach(dat,2)
> search()
 [1] ".GlobalEnv"        "dat"               "package:tools"     "package:lattice"
 [5] "tools:rstudio"     "package:stats"     "package:graphics"  "package:grDevices"
 [9] "package:utils"     "package:datasets"  "package:methods"   "Autoloads"
[13] "package:base"
> f <- function(){
+    g <- function() x
+    x <- 3
+    g}
> h <- f()
> g <- function()x
> ls()
[1] "dat" "f"   "g"   "h"
> h()
[1] 3
> g()
[1] 2
> detach(dat)
> h()
[1] 3
> g()
Error in g() : object 'x' not found

-- Bert


On Tue, Apr 4, 2023 at 6:56 AM akshay kulkarni <akshay_e4 using hotmail.com<mailto:akshay_e4 using hotmail.com>> wrote:
Dear Members,
                             I have the following code typed at the console prompt:

y   <-   x*10

X has not been defined and the above code throws an object not found error. That is, the global environment does not contain x. Why doesn't it look further in the environment stack, like that of packages? There are thousands of packages that contain the variable named  x. Of course, that happens if the above code is in a function (or does it?).

What concept of R is at work in this dichotomy?

THanking you,
Yours sincerely,
AKSHAY M KULKARNI

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